Method of drying leather



Patented Mar. 27, 1934 PATENT OFFICE METHOD OF DRYING LEATHER Matthew M. Merritt, Middleton, Mass, assignor to The Tanning Process Company, Boston, Mass, a corporation of Massachusetts No Drawing. Application April 2'7, 1933, Serial No. 668,292

12 Claims.

This invention relates to methods of drying skins and particularly to the drying of skins after tanning operations thereon. While the invention is described with referenceto a method of '5 drying skins wherein marginal portions thereof lowing the tanning and/or dyeing operation.

are secured by an adhesive to drying boards, it is to be understood that the invention and important characteristics thereof may have various applications and uses.

Objects of this invention are to speed up the operation of drying skins and to secure a better product with less labor and at a minimum of expense.

To these ends and in accordance with an important characteristic of the invention a skin is slicked-out upon a portable work support having a smooth work supporting surface, the purpose" being to secure the full extended area of the skin and to remove a large part of the watery content thereof. Preferably the slicking out operation is performed promptly after the tanning and/or dyeing operation while the skin is still quite wet with wash water from the washingoperation fol- Under these conditions, a large part of the watery content of the skin may be more easily removed and the skin is much more likely to yield the maximum area upon slicking-out, than would be the case if the skin had been allowed to drain for hours and thus become partly dry in 'acbordance with the prior practice. Promptly after the slicking-outoperation the portable work support with the skin thereon is transferred to a drying board or support where the skin may be separated from the portable support'and left in fully extended condition upon the drying board. Preferably the portable work support is also flexible so that, following the putting-out operation on said flexible and portable work support, the skin may be transferred to a drying board by stripping or peeling the flexible work support i, from the skin while the latter is lying in fully extended condition on the drying board. Mar- 'ginal portions of the skin may be secured to the 'drying board as, for example, by staples or by adhesive strips of paper attached partly to the flesh surface of the marginal portions of the skin and to the adjacent surface of the drying board. In accordance with a preferred method of drying the skins aftertanning and/or dyeing operations'the skins are slicked-out upon a portable work support with the grain surface down, after which an adhesive is applied to the exposed flesh surface of the skin Then the portable work support and skin are transferredto a drying board with the flesh surface of the skin in contact with said board after which the portable work support is removed leaving the skin in fully spread-' out condition on the drying board, the portable work support being preferably flexible so that it may be stripped from the skin while the latter is in contact with the drying board. In practice the adhesive is applied to marginal portions only of the flesh surface of the slicked-out skin, preferably throughout substantially the entire periphery thereof, since by this operation the marginal portions of the skin will dry only after all the rest of the skin has dried thereby reducing to a minimum curling of the edges of the skin during drying. Since the'exposed grain surface is denser than the flesh surface, it dries in about the same time as the flesh surface in contact with the drying board. This fact accounts in part for the relatively short time consumed and the excellent results secured in the described drying operation.

It has been found that the amount of adhesive to be applied to the marginal portions of the skin in order to secure the desired results is relatively so small that ordinarily it need not be removed from the flesh surface of the skin, it being clear that the grain surface of the skin is left in perfect condition since no adhesive reaches the grain surface.

These and other important characteristics of the method will now be described in detail in the scpecification and pointed out more particularly in the appended claims.

In the practice of the method a skin, which has been washed after coming fresh from the tan ning and/or dyeing vat or drum, is spread out more or less carefully upon a flexible mat made of rubber or of some other substance havinga similar degree of flexibility and resiliency. The mat with the skin spread out thereon is then introduced into a putting-out machine of a common commercial type, for example, such as that shown in United States Letters Patent No. 1,344,- 467, granted June 22, 1920, upon application of R. F. Whitney, comprising characteristically a bed roll, a bladed cylinder for operating on the work supported by the bed roll, and a feed roll arranged for co-operation with the bed roll in feeding the work past the bladed cylinder; The mat with the piece of work is introduced into the machine, while the latter is in open or work receiving position, to such an extent that approximately one-half of the skin will beoperated upon while the mat and skin are being fed by the co-operation of the bed roll and feed roll. Subsequently the mat and skin are reinfrom. It will be understood that the skin may be slicke'd-out upon the mat by hand, using a manually operable slicker blade, or by some other suitable machine other than that described.

The mat with the slicked-out skin thereon is promptly transferred by a conveyor, or otherwise to a station where an adhesive is applied to the exposed flesh surface of the skin. I have found that a suitable adhesive may be made from ordinary wheat flour, and then thinned so that it may be applied by a small spray gun. It will be understood that any of the well-known dextrins or starches may be utilized in making a suitable adhesive. While the adhesive may be applied all over the exposed surface in a very thin layer, as by a spraying device, it is preferred to apply the adhesive only to the marginal portions of the entire periphery of the skin. In other words, the adhesive is applied along a strip an inch (more or less) in width, extending entirely around the periphery of the skin, or substantially so, the quantity of adhesive being sufficient to insure that the skin will adhere to a drying board during the drying operation. Since the skin has the greater portion of the water removed therefrom during the putting-out operation the adhesive will not be unduly diluted when applied to the marginal portions of the slicked-out skin, On the other hand, the skin should be moist enough so that the adhesive will come into such intimate contact therewith as to unite with the flesh surface of the skin. if the skin were too dry on its flesh surface there would not be enough moisture on the surface to flow the adhesive into the desired intimate contact with the fibers or other minute structure of the flesh surface of the skin.

Promptly after the application of the adhesive in the manner described, the mat with the skin thereon is transferred to a drying .ioard with the skin in contact with the latter. Preferably, the mat, with its adhering skin, is placed upon the drying board and the adhesively coated skin is forced into firm contact with the surface of the drying board. In practice, the skin, with its adhesively coated marginal portions, is forcibly slapped upon the drying board while still in extended condition upon its carrying mat. Then the flexible mat is stripped or peeled back from the skin, leaving the latter in fully extended condition on the drying board and with its marginal portions sealed to the board by the adhesive. It is to be understood that the whole flesh surface is brought into intimate contact with the drying board at thesame time that the marginal portions thereof are caused to adhere to said board. The drying board with the skin thereon may be transferred by a movable support or by a conveyor to a station where a finishing touch may be given to the skin to insure that all the marginal portions of the skin are adhering properly to the drying board. This drying board is subsequently returned to position to receive another skin on its opposite face applied in the same manner as above described. The drying board is then hung up in a drying loft for the skins to dry thereon at ordinary room temperatures. The drying takes place promptly, the marginal portions being the last to dry whereby the skin is maintained in extended condition during the drying operation.

If desired some other securing means may be employed to secure the skins to the drying board. That is, in special cases, it maybe desirable to use staples or strips of adhesive paper to secure the skins in place on the'drying board, instead of the adhesive described. However, the latter is cheaper, more easily applied, and highly effective in connection with skins properly tanned and otherwise properly treated.

.This application is a continuation in part of my copening application Serial No. 570,967, filed Oct. 24, 1931.

Having described my invention, what I claim as new and desireto secure by Letters Patent of the United States is:

1. That improvement in methods of treating skins which comprises tanning a skin, while still wet after the tanning operation slicking the skin out in fully extended condition upon a portable work support having a smooth work supporting surface, transferring the portable work support and the skin in slicked-outcondition thereon to a position over a drying board or support with the skin resting on the drying support, and then separating the skin from the work support-sothat it rests on the drying support in fully slickedout condition thereon. i

2. That improvement in methods of treating skins which comprises subjecting the skins to a tanning preparation until they have been thoroughly tanned, while still wet after, the tanning operation subjecting each skin to a slicking-out operation upon a flexible. portable work support having a smooth work supporting surface, transferring the portable work support with the skin slicked-out thereon to a drying board or support with the slicked-out skin rest-ing upon the drying support, and then strippingthe flexible portable work support from the skin whereby the latter is leftin fully extendedcondition upon the drying support. j

3. That improvement in methods of treating skins which comprises subjecting the skins to a tanning preparation until they have been thor-; oughly'tanned, while still wet after the tanning operation subjecting each skin to a slicking-out operation upon a flexible portable work;support having a smooth work supporting surface, with the grain surface of the skin in contact with the work support, transferring the portable Work support with the skin slicked-out thereon to a drying board or support with the flesh surface of the slicked-out skin resting upon the drying support, and then stripping-the flexible portable work support from the skin whereby the latter is left in fully extended condition upon the dry? ing support.

i; That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition and with its grain-surface .down upon a smooth supporting surface, applying an adhesive to the flesh surfaceof the clicked-out skin, and transferring the skin in its extended condition to another worksupporting surface with the adhesively coated flesh surface in contact with said supporting surface where the :skin may dry in its extended condiiton. v

5. That. improvement in methods of drying skins which comprises slicking askin outin fully extended condition with its grain surface in; .contact with a portable work support,..applying-an adhesive to theflesh surface .of:-.the slicked-out skin, transferring the work support and skin to a drying board, and causing the skn to adhere to the drying board in its fully slicked-out condition where it may be allowed to dry.

6. That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition and with ts grain surface down upon a flexible mat, applying an adhesive to the flesh surface of the slicked-out skin, transferring the skin, while in its extended condition on the mat, to a drying board wth the adhesively coated flesh surface in contact with said board, and stripping the flexible mat from the skin leaving the latter on the drying board to dry.

7. That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition with its grain surface in contact with a flexible mat, applying an adhesive to the flesh surface of the slicked-out skin, forcing the adhesively coated skin, while still spread out on its mat, into firmcontact with a drying board, and stripping the flexible mat from the skin leaving it to dry on the drying board in its fully slicked-out condition.

8. That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition with its grain surface in contact with a work support, and promptly transferring the skin to a drying board in its fully slicked-out condition and with the grain side out, wherebydrying takes place from the grain side.

9. That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition with its grain surface in contact witha flexible mat, applying an adhesive to the flesh surface of the marginal portions only of the slicked-out skin throughout substantially the entire periphery thereof, applying the adhesively coated skin forcibly to a drying board while the skin is still on the mat in its fully slicked-out condition, and stripping the flexible mat from the skin.

10. That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition with its grain surface in contact with a flexible mat, applying an adhesive to the flesh surface of the marginal portions only of the skin throughout substantially the ;entire periphery thereof, transferring the mat with its spread-out skin to a drying board with the flesh surface of the skin in contact with said board, forcing the skin into firm contact with the drying board, and stripping the flexible mat "away from the skin, leaving the latter to dry in fully extended condition on the drying board.

11. That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition with its grain surface in contact with a flexible mat, applying an adhesive to the flesh surface of the slicked-out skin, and slapping the mat and skin forcibly against a drying board to transfer the skin from the mat to the drying board, where it may be allowed to dry.

12. That improvement in methods of drying skins which comprises slicking a skin out in fully extended condition with its grain surface in contact with a flexible mat, applying an adhesive to the flesh surface of the marginal portions only of the skin throughout substantially the entire periphery thereof, slapping the mat and skin forcibly against a drying board to transfer the skin from the mat to the drying board, and stripping the flexible mat from the skin, thus leaving the latter to dry in fully extended condition on the drying board.

MATTHEW M. MERRITI. 

